Measuring Cellphone battery voltage problem

[hardcore misery]

Duff charger circuit?.

How do you know the battery is overcharged?.

as an example, my cell battery(a BL-4C battery for nseries and 60 series nokia phones) expanded its size(looks mutated) and its life span was lessened, i don't have a picture my battery, but i think you can visualized what i've stated.

as for the li-ion batteries for nokia 3310's, i've seen some expanded batteries.

 

[Nigel Goodwin]

Sounds like the charging circuits died then, usually an important part of the charging circuit monitors the temperature of the battery, and if it gets too hot then shuts it down.

 

[audioguru]

The battery is a Lithium-Ion type. The 3rd contact is its temperature sensor.

 

[sam2]

The only time I have seen or read about repeat problems with lithium batteries in consumer electronics is, from defective batteries (real namebrand ones) or, and these are the most common, bogus, bootleg namebrand or just cheap crap from China.

 

[hardcore misery]

The battery is a Lithium-Ion type. The 3rd contact is its temperature sensor.

what do you mean by the 3rd contact? is it on the center?, on our charger circuit, will be going to use the 1st and 3rd contacts (indicated with + and -)

 

[audioguru]

The temperature sensor is the middle contact but I don't have any spec's on it.

 

[sam2]

what do you mean by the 3rd contact? is it on the center?, on our charger circuit, will be going to use the 1st and 3rd contacts (indicated with + and -)

As johnny storm would say... Flame on!

https://www.youtube.com/watch?v=SQ0SNESIkWk&mode=related&search=

https://www.youtube.com/watch?v=vE532lRT3kw&NR=1

 

[hardcore misery]

As johnny storm would say... Flame on!

https://www.youtube.com/watch?v=SQ0SNESIkWk&mode=related&search=

https://www.youtube.com/watch?v=vE532lRT3kw&NR=1

horrible... is it safe to use, 6V / 300mAh charger on li-ion batteries?(3.7V)

 

[audioguru]

horrible... is it safe to use, 6V / 300mAh charger on li-ion batteries?(3.7V)

Of course not!
Then the battery will over-charge and will catch on fire.

You need a Li-Ion battery charger IC that limits the current and stops the charging when the voltage reaches the manufacturer's recommendations.
It has a backup circuit that uses the temperature sensor in the battery to stop charging when it gets too hot.
It has a low voltage detector that reduces the charging current to a battery that has been discharged too low.

The cell phone has this IC inside.

 

[hardcore misery]

Of course not!
Then the battery will over-charge and will catch on fire.

You need a Li-Ion battery charger IC that limits the current and stops the charging when the voltage reaches the manufacturer's recommendations.
It has a backup circuit that uses the temperature sensor in the battery to stop charging when it gets too hot.
It has a low voltage detector that reduces the charging current to a battery that has been discharged too low.

The cell phone has this IC inside.

so if we can't avail this maxim IC, can we use at least 3.7V to 4.2V(300maH) specs on our charger circuit?

 

[audioguru]

Is the max charged voltage of the battery 4.1V or 4.2V?
What is the recommended charging current for the battery?
What are the spec's for the temperature sensor in the battery?

All you are doing is repeating what the cell phone designer has done to make the charger. Except you probably won't be able to find out what is the recommended voltage and current and details about the temperature sensor for the battery.

 

[hardcore misery]

the max. voltage for a li-ion cell battery is 4.2V

on our charger, i've set the charging voltage to 3.9V - 4V with 400mAH (clarification: to limit the output current of a power supply, a series resistor on the ground should be placed? 4V / 10ohms = 400mA)

we don't have temperature sensor for the charger circuit.

if we have 3.9V as a charger voltage, does the battery voltage reaches at 4.2V? even though the charging voltage is lower than 4.2V?

 

[audioguru]

The battery won't be anywhere near fully charged when the charging voltage is only 3.9V without a load. The voltage will be lower with the battery connected because your 10 ohms resistor isn't a current regulator.

The 10 ohm resistor limits the current to 400mA for a dead short. When the battery voltage reaches 3.0V then the 10 ohm resistor limits the current to only 100mA. When the battery voltage reaches 3.5V then the 10 ohms resistor limits the current to only 50mA. You need an active current regulating circuit to provide 400mA until the battery voltage reaches 4.2V.

You must use temperature sensing circuit to avoid a fire and manufacturers of Li-Ion batteries also recommend timers as another backup.

Read all about one manufacturer's Li-Ion battery charging here:
https://www.panasonic.com/industrial/battery/oem/chem/lithion/index.html

EDIT: Panasonic shows that their Li-Ion cells are only half charged when the voltage reaches only 3.9V.

 

[sam2]

Look here too: https://shdesigns.org/lionchg.html

But you cant just hook this up to your cell phone, because it allready has a charger built in.

This will give you some idea what is needed for charging lithium batteries but, it has no extra safety features.

sam

 

[audioguru]

I forgot to say that when the battery voltage reaches 4.2V then it is 90% fully charged. It needs another 40 minutes at 4.2V for its charging current to automatically drop to 100mA when it will be 100% fully charged.

 

[hardcore misery]

The battery won't be anywhere near fully charged when the charging voltage is only 3.9V without a load. The voltage will be lower with the battery connected because your 10 ohms resistor isn't a current regulator.

The 10 ohm resistor limits the current to 400mA for a dead short. When the battery voltage reaches 3.0V then the 10 ohm resistor limits the current to only 100mA. When the battery voltage reaches 3.5V then the 10 ohms resistor limits the current to only 50mA. You need an active current regulating circuit to provide 400mA until the battery voltage reaches 4.2V.

You must use temperature sensing circuit to avoid a fire and manufacturers of Li-Ion batteries also recommend timers as another backup.

Read all about one manufacturer's Li-Ion battery charging here:
https://www.panasonic.com/industrial/battery/oem/chem/lithion/index.html

EDIT: Panasonic shows that their Li-Ion cells are only half charged when the voltage reaches only 3.9V.

how did you compute this? at NO LOAD the limited current is 400mAH...

when there's a load with 3.7V, the limited is equal to 370maH? or
400maH - 370mAH = 130maH?

 

[audioguru]

how did you compute this? at NO LOAD the limited current is 400mAH...

when there's a load with 3.7V, the limited is equal to 370maH? or
400maH - 370mAH = 130maH?

At no load then there isn't any current.
When the supply is 4.0V then a dead short creates a current in the 10 ohms resistor of 400mA.
When the battery voltage rises to 3.0V then the resistor has 1.0V across it and Ohm's Law calculates the current to be only 100mA.
When the battery voltage rises to 4.0V then there won't be any current but the battery will not be fully charged.

You need to have an active current regulator to keep the current steady while the battery is charging. A simple resistor won't do it.